IIRC there's no retention date. Meaning Amazon can keep your voice recording for as long as they want without needing to delete it.
I imagine the EU will pass some privacy law that the rest of the world will then follow surrounding this.
Fwiw Apple does this for Siri, Google does this for their assistant, as does Microsoft.
It's mostly for training their AI to recognize words in different accents, tibres, and variations.